if you don't have it (password will be required) and go to general options>desktop size and change to whatever you require (if you're going to use the cube plugin, you have to have vertical size as 1, horizontal can be anything you like).

You can also use gconf-editor which is a bit harder to use but is probably installed already. Open it up from a terminal or alt+f2 and go to apps>compiz>general>screen0>options and change the hsize and vsize attributes.

I'd recommend using version 10.04 at the very least, 10.10 preferably as it fixes a few irritants (you don't have to reinstall, you can upgrade). There are tons of advantages to using post-10.04 Ubuntu, not least a well needed appearance overhaul and the addition of indicator apps to replace the systray.

Oh, it would also depend on your graphics card and whether it supports 3D and which driver it is currently using.

Edit II: The Musical: It just occurred to me that you might mean how do you use it, in which case ctrl+alt + a direction key (left or right, up or down depending on how you've configured it). There are probably mouse actions too, but I don't use one often enough to remember. You can, of course, reconfigure to your liking.

Sorry.

Edit III: The Next Generation: You can also install a simple CCSM from the repositories (using the same apt-get command as above). It's called simple-ccsm.